basalt - hand/display specimen of amygdaloidal basalt

$ 7.50

Basalt is commonly vesicular, filled with empty bubbles that form when dissolved gases and water come out of solution as the pressure drops in a magma during an eruption, much as bubbles form in a shaken soda when the can is opened and the pressure is released.

Basalt is porous and if hydrothermal fluids pass through the flow, the vesicles can be filled with quartz, calcite or any of a number of zeolite minerals. The filled vesicles are called amygdales. A basalt with amygdales is amygdaloidal.

Amygdale's etymology is interesting. Amygdale is Greek for almond. In 15th century English, amygdales meant "the tonsils." The amygdales in this basalt are only almond shaped if you use a lot of imagination.

Zeolites are microporous aluminosilicates. The name is from the Greek zeo meaning to boil, and lithos, meaning stone. In 1756, Swedish mineralogist Axel Fredrik Cronstedt coined the name when he observed that strongly heating a zeolite with a blowpipe produced large amounts of steam from water it had absorbed. The mineralogy of the amygdales in this basalt is undetermined.

This basalt is from a Neogene (Quaternary) flow at the northern end of the Coso Range in Inyo County, California. As you can see from the QAPF diagram, the compositions of basalt and andesite can overlap and both are variable within the yellow polygon in the diagram.

 

 

 

Select a specimen: You can select a specimen by telling us what is in the photo with it,  a black mechanical pencil or pencil plus some number of coins, or you can let us make the selection.

Making multiple purchases? Click on the "combine shipping" button in the shopping cart. We'll send an invoice with combined shipping. A link in that invoice will bring you back to checkout, no hassle.

Ships in a Regional Priority Mail box. There would be room in that box for other specimens at no increase in postage. Please request an invoice to avoid overpaying shipping, by clicking the "combine shipping" button in the cart.  Click > Shipping < for shipping rates. Use back button to return to this page.